ive had 2 of the same problems when i would get on my car to go threw a light than let off, it would sound like its backfiring, i ended up having a 3 inch downpipe (catted) and it doesnt do it anymore. the choppy idle is most likely a vacuum leak, i still havent fixed it, its on the list, and the hesitation, is probably a MAF sesnor if it bucks feels like its gonna stall etc.

hope I helped - ryan